Tag Archives: HWISI

Helene Intensifies to a Major Hurricane

Hurricane Helene intensified to a major hurricane over the eastern Gulf of Mexico on Thursday.  At 2:00 p.m. EDT on Thursday the center of Hurricane Helene was located at latitude 26.7°N and longitude 84.9°W which put the center about 205 miles (335 km) south of Apalachicola, Florida.  Helene was moving toward the north-northeast at 16 m.p.h. (26 km/h).  The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 140 m.p.h. (225 km/h).  The minimum surface pressure was 959 mb.

A Hurricane Warning is in effect for the portion of the coast from Anclote River to Mexico Beach, Florida.

A Hurricane Watch is in effect for the portion of the coast from Anclote River to Englewood, Florida.  The Hurricane Watch includes Tampa Bay.

A Tropical Storm Warning is in effect for the portion of the coast from Anclote River to Flamingo, Florida.  The Tropical Storm Warning includes Tampa Bay.  A Tropical Storm Warning is in effect for the Lower and Middle Florida Keys west of Channel 5 Bridge.  A Tropical Storm Warning is in effect for the Dry Tortugas.  A Tropical Storm Warning is in effect for the portion of the coast from Mexico Beach to the Okaloosa/Walton County Line, Florida.  A Tropical Storm Warning is in effect for the portion of the coast from Flamingo, Florida to Little River Inlet, South Carolina.  A Tropical Storm Warning is in effect for Lake Okeechobee. 

A U.S. Air Force Hurricane Hunter aircraft found that Hurricane Helene had strengthened to a major hurricane on Thursday afternoon.  An eye with a diameter of 30 miles (48 km) was at the center of Helene’s circulation.  The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the center of Hurricane Helene.  Storms near the center of Helene generated strong upper level divergence that pumped large quantities of mass away from the hurricane.

The circulation around Hurricane Helene was large.  Winds to hurricane force extended out 60 miles (95 km) from the center of Helene’s circulation.  Winds to tropical storm force extended out 345 miles (555 km) in the eastern side of Hurricane Helene.  Winds to tropical storm force extended out 140 miles (225 km) in the western side of Helene’s circulation.

The Hurricane Intensity Index (HII) is 22.1.  The Hurricane Size Index (HSI) is 17.6 and the Hurricane Wind Intensity Size Index (HWISI) 39.7.  Hurricane Helene is stronger than Hurricane Irma was when Irma hit southwest Florida in 2017.  However, Helene is not as big as Irma was.

Hurricane Helene will move through an environment favorable for intensification during the next few hours.  Helene will move over water where the Sea Surface Temperatures are near 30°C.  It will move under the middle of an upper level ridge over the eastern Gulf of Mexico.  The upper level winds are weak near the middle of the ridge and there will be little vertical wind shear.  Hurricane Helene is likely to intensify during the next few hours.  Helene could strengthen to Category 4 on the Saffir-Simpson Scale.

Hurricane Helene will move around the western end of a high pressure system over the western Atlantic Ocean.  The high pressure system will steer Helene toward the north-northeast during the next 24 hours.  On its anticipated track, Hurricane Helene will make landfall on the coast of northern Florida at Apalachee Bay Thursday evening.  Helene will be a major hurricane when it reaches the coast.

Hurricane Helene will be a major hurricane when it reaches northern Florida.  Helene will be a large and dangerous hurricane.  Hurricane Helene will bring strong winds and heavy rain to northern Florida.  Heavy rain is likely to cause floods.

Flood Watches are in effect for Florida, eastern Alabama, Georgia, western South Carolina, western North Carolina and eastern Tennessee.

Helene could also cause a storm surge of up to 20 feet (6.1 meters) along portions of the west coast of Florida.

A Storm Surge Warning is in effect for the portion of the coast from Mexico Beach to Flamingo, Florida.  The Storm Surge Warning includes Tampa Bay and Charlotte Harbor.

An upper level trough over the Mississippi River Valley will steer Hurricane Helene quickly toward the north-northeast after it makes landfall.  Since the circulation around Helene is so large, Hurricane Helene will produce hurricane force winds in inland locations as well.

Hurricane Warnings are in effect for parts of northern Florida, southeastern Alabama and southwestern Georgia.  The Hurricane Warnings include Tallahassee, Florida and Macon, Georgia.

Tropical Storm Warnings are in effect for the Florida Peninsula, northwest Florida eastern Alabama, northern and eastern Georgia, all of South Carolina, southwestern North Carolina, and southeastern Tennessee.  The Tropical Storm Warnings include Atlanta, Georgia and Charleston, South Carolina.

Hurricane Helene is likely to cause widespread electricity outages as it moves inland over the southeastern U.S.

Hurricane John Hits Mexico

Rapidly intensifying Hurricane John hit the coast of Mexico near Punta Maldonado on Monday night.  At 11:00 p.m. EDT on Monday the center of Hurricane John was located at latitude 16.3°N and longitude 98.8°W which put the center about 15 miles (25 km) west of Punta Maldonado, Mexico.   John was moving toward the north at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 140 m.p.h. (225 km/h).v  The minimum surface pressure was 959 mb.

A Hurricane Warning was in effect for the portion of the coast from Acapulco to Bahias de Huatulco, Mexico.

A Tropical Storm Warning was in effect for the portion of the coast from Bahias de Huatulco to Salina Cruz, Mexico. 

Hurricane John rapidly intensified to a major hurricane as it approached the coast of Mexico near Punta Maldonado on Monday night.  A circular eye with a diameter of 6 miles (10 km) was at the center of John’s circulation.  The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Hurricane John.

The circulation around Hurricane John was very small.  Winds to hurricane force extended out 15 miles (25 km) from the center of John’s circulation.  Winds to tropical storm force extended out 45 miles (75 km) from the center of Hurricane John.

The Hurricane Intensity Index (HII) for Hurricane John was 22.1  The Hurricane Size Index (HSI) was 4.1 and the Hurricane Wind Intensity Size Index (HWISI) was 26.1.  Hurricane John was capable of causing localized major damage.

Hurricane John will move inland over eastern Guerrero and western Oaxaca on Tuesday.  John will bring strong winds and heavy rain to the region around Punta Maldonado.  Heavy rain is likely to cause flash floods in some locations.  Hurricane John could also cause a storm surge of up to 12 feet (3.6 meters) along the coast near Punta Maldonado.

Hurricane John will weaken very quickly as it moves inland because of the small size of its circulation.  Even though John will weaken quickly, it will still drop heavy rain over parts of eastern Guerrero and western Oaxaca.  Flash floods are likely to occur in that region on Tuesday before Hurricane John dissipates.

Hurricane Francine Brings Wind and Rain to Southeast Louisiana

Hurricane Francine brought wind and rain to southeast Louisiana on Wednesday evening.  Francine weakened to a tropical storm after it moved inland.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Francine was located at latitude 30.2°N and longitude 90.6°W which put the center about 35 miles (55 km) west-northwest of New Orleans, Louisiana.  Francine was moving toward the northeast at 16 m.p.h. (26 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 85 m.p.h. (135 km/h).  The minimum surface pressure was 982 mb.

A Tropical Storm Warning is in effect for the portion of the coast from Intracoastal City, Louisiana to the Alabama/Florida border.  The Tropical Storm Warning includes New Orleans, Lake Pontchartrain and Lake Maurepas.

Francine was a Category 2 Hurricane on the Saffir-Simpson Scale at the time of landfall.  The maximum sustained wind speed at that time was 100 m.p.h. (160 km/h).  At the time of landfall winds to hurricane force extended out 40 miles (65 km) from the center of Francine’s circulation.  Winds to tropical storm force extended out 140 miles (220 km) from the center of circulation.

The Hurricane Intensity Index (HII) at landfall was 16.5.  The Hurricane Size Index (HSI) was 13.7 and the Hurricane Wind Intensity Size Index (HWISI) was 30.2.  Hurricane Francine was similar in intensity to Hurricane Idalia when Idalia hit Florida in 2023.  Francine was larger than Idalia was.

The center of Hurricane Francine made landfall on the coast of Louisiana south-southwest of Morgan City.  The center passed near a NOAA National Ocean Service Station north of Eugene Island, Louisiana (EINL1).  The station reported a sustained wind speed of 75 m.p.h. (120 km/h) and a wind gust of 105 m.p.h. (169 km/h).  The station reported a surface pressure of 976.0 mb.

The center of former Hurricane Francine passed west of New Orleans.  Francine dropped heavy rain over many parts of southeast Louisiana.  Flash Flood Warnings were issued for several parishes.  A weather station at the Louis Armstrong International Airport received 6.98 inches (177.3 mm) of rain.  A weather station at New Orleans Lakefront Airport reported 4.58 inches (116.3 mm) or rain.  Heavy rain was beginning to fall over parts of southern Mississippi.

Southerly winds were still pushing water toward the coast of southeast Louisiana and the coast of Mississippi.  Those winds were causing a storm surge along the coast.

A Storm Surge Warning in in effect for the portion of the coast from Avery Island, Louisiana to the Mississippi/Alabama border.  The Storm Surge Warning includes Vermilion Bay, Lake Pontchartrain and Lake Maurepas.

Tropical Storm Francine will move between a high pressure system that extends from the western Atlantic Ocean to the Gulf of Mexico and an upper level trough over the South Central U.S.  The high pressure system and the upper level trough will steer Francine toward the north-northeast during the next 24 hours.  On its anticipated track, the center of Tropical Storm Francine will move across Mississippi on Thursday.

Tropical Storm Francine will continue to weaken as it moves farther inland.  Even though Francine will weaken it will bring strong winds and heavy rain to southeastern Louisiana, Mississippi, South Alabama and Northwest Florida.  Heavy rain is likely to cause floods in some locations.

Flood Watches are in effect for parts of Louisiana, Mississippi, Alabama and Northwest Florida.

 

Hurricane Francine Strengthens to Cat. 2

Hurricane Francine strengthened to Category 2 on the Saffir-Simpson Scale on Wednesday afternoon as it neared southeast Louisiana.  At 5:00 p.m. EDT on Wednesday the center of Hurricane Francine was located at latitude 29.2°N and longitude 91.5°W which put the center about 40 miles (65 km) south-southwest of Morgan City, Louisiana.  Francine was moving toward the northeast at 17 m.p.h. (28 km/h).  The maximum sustained wind speed was 100 m.p.h. (160 km/h) and there were wind gusts to 120 m.p.h. (195 km/h).  The minimum surface pressure was 972 mb.

A Hurricane Warning is in effect for the portion of the coast from the Vermilion/Cameron Parish Line to Grand Isle, Louisiana

A Hurricane Watch is in effect for New Orleans, Lake Pontchartrain and Lake Maurepas.

A Tropical Storm Warning is in effect for the portion of the coast from Cameron to the Vermilion/Cameron Parish Line, Louisiana.  A Tropical Storm Warning is in effect for the portion of the coast from Grand Isle, Louisiana to the Alabama/Florida border.  The Tropical Storm Warning includes New Orleans, Lake Pontchartrain and Lake Maurepas.

Data from reconnaissance aircraft in Hurricane Francine on Wednesday afternoon indicated that Francine had strengthened to a Category 2 Hurricane.  A large circular eye with a diameter of 45 miles (75 km) was at the center of Francine’s circulation.  The eye was surrounded by a broken ring of thunderstorms and the strongest winds were occurring in that ring of storms.  Thunderstorms were occurring in bands in the northern and eastern sides of Francine’s circulation.  Bands in the southern and western sides of Hurricane Francine consisted primarily of showers and lower clouds.

The center of Hurricane Francine appeared to wobble slightly to the east as it approached the coast of Louisiana.  The northern part of the eyewall  of Hurricane Francine was moving over the coast of southeast Louisiana south of Morgan City.  A NOAA National Ocean Service station north of Eugene Island, Louisiana (EINL1) reported a sustained wind speed of 75 m.p.h. (120 km/h) and a wind gust of 99 m.p.h. ((160 km/h).  The station reported a surface pressure of 981.4 mb.

The strongest winds were occurring southeast of the center of Hurricane Francine.  Winds to hurricane force extended out 40 miles (65 km) from the center of Francine’s circulation.  Winds to tropical storm force extended out 140 miles (220 km) from the center of Hurricane Francine.

The Hurricane Intensity Index (HII) was 16.5.  The Hurricane Size Index (HSI) was 13.7 and the Hurricane Wind Intensity Size Index (HWISI) was 30.2.  Hurricane Francine was similar in intensity to Hurricane Idalia when Idalia hit Florida in 2023.  Francine was larger than Idalia was.

Hurricane Francine will move between a high pressure system that extends from the western Atlantic Ocean to the Gulf of Mexico and an upper level trough over the South Central U.S,  The high pressure system and the upper level trough will steer Francine toward the northeast during the next 24 hours.  On its anticipated track, the center of Hurricane Francine will make landfall on the southeast coast of Louisiana late during the next several hours.  Francine will move across southeast Louisiana on Wednesday night.

Hurricane Francine will bring strong winds and heavy rain to Louisiana.  Heavy rain was already falling on many places in southeast Louisiana.  Francine will be capable of causing serious damage.  Widespread outages of electricity are likely.  Heavy rain is likely to cause floods.  The heaviest rain will fall as the center of Francine’s circulation approaches a given location.   Hurricane Francine will also drop heavy rain over parts of Mississippi, South Alabama and Northwest Florida as it moves inland.

Flood Watches are in effect for parts of Louisiana, Mississippi, Alabama and Northwest Florida.

Hurricane Francine could cause a storm surge of up to 10 feet (3 meters) along parts of the coast of Louisiana.  The highest surge will occur just to the east of where the center of Francine makes landfall in southeast Louisiana.  The storm surge will continue after the center of Hurricane Francine makes landfall because southerly winds will continue to push water toward the coast.

A Storm Surge Warning is in effect for the portion of the coast from Cameron/Vermilion Parish Line, Louisiana to the Mississippi/Alabama border.  The Storm Surge Warning includes Vermilion Bay, Lake Pontchartrain and Lake Maurepas.

 

Hurricane Francine Nears Louisiana

Hurricane Francine neared the coast of Louisiana on Wednesday morning.  At 11:00 a.m. EDT on Wednesday the center of Hurricane Francine was located at latitude 28.0°N and longitude 92.7°W which put the center about 150 miles (240 km) southwest of Morgan City, Louisiana.  Francine was moving toward the northeast at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 90 m.p.h. (145 km/h) and there were wind gusts to 105 m.p.h. (165 km/h).  The minimum surface pressure was 976 mb.

A Hurricane Warning is in effect for the portion of the coast from the Vermilion/Cameron Line to Grand Isle, Louisiana

A Hurricane Watch is in effect for New Orleans, Lake Pontchartrain and Lake Maurepas.

A Tropical Storm Warning is in effect for the portion of the coast from Sabine Pass to the Vermilion/Cameron Line, Louisiana.  A Tropical Storm Warning is in effect for the portion of the coast from Grand Isle, Louisiana to the Alabama/Florida border.  The Tropical Storm Warning includes New Orleans, Lake Pontchartrain and Lake Maurepas.

Hurricane Francine maintained its intensity as it moved closer to the coast of Louisiana on Wednesday morning.  An upper level trough over the South Central U.S. was producing southwesterly winds that were blowing toward the top of Francine’s circulation.  Those winds were causing the vertical wind shear to increase.  In addition, the circulation around the western side of Hurricane Francine was pulling drier air into the southern part of Francine’s circulation.  Francine maintained its intensity even with the effects of the increased wind shear and drier air.

The effect of the vertical wind shear and the drier air also affected the structure of Hurricane Francine.  A large circular eye with a diameter of 45 miles (75 km) was at the center of Francine’s circulation.  The eye was surrounded by a broken ring of thunderstorms and the strongest winds were occurring in that ring of storms.  The break in the ring of thunderstorms was south of the eye of Hurricane Francine.  Storms near the center of Francine generated upper level divergence that pumped mass away to the northeast of the hurricane.  The removal of mass in the upper levels almost balanced the inflow of mass in the lower levels and the surface pressure remained nearly steady.

The wind shear and drier air also affect the distribution of thunderstorms in Hurricane Francine.  Thunderstorms were occurring in bands in the northern and eastern sides of Francine’s circulation.  Bands in the southern and western sides of Hurricane Francine consisted primarily of showers and lower clouds.

The size of the circulation around Hurricane Francine remained steady.  Winds to hurricane force extended out 40 miles (65 km) from the center of Francine’s circulation.  Winds to tropical storm force extended out 115 miles (185 km) from the center of Hurricane Francine.

The Hurricane Intensity Index (HII) for Hurricane Francine was 13.9.  The Hurricane Size Index (HSI) was 13.5 and the Hurricane Wind Intensity Size Index (HWISI) was 27.4.  Hurricane Francine was similar in size and intensity to Hurricane Hanna when Hanna hit South Texas in 2020.

Hurricane Francine will move through an environment marginally favorable for intensification during the next 18 hours.  Francine will move over water where the Sea Surface Temperatures are near 30°C.  However, the upper level trough over the South Central U.S. will cause moderate vertical wind shear.  The drier air in the southern half of Francine’s circulation will also inhibit intensification.  Hurricane Francine is likely to maintain its current intensity during the next few hours until it reaches Louisiana.

Hurricane Francine will move between a high pressure system that extends from the western Atlantic Ocean to the Gulf of Mexico and the upper level trough over the South Central U.S,  The high pressure system and the upper level trough will steer Francine toward the northeast during the next 24 hours.  On its anticipated track, the center of Hurricane Francine will make landfall on the southeast coast of Louisiana late on Wednesday afternoon.

Hurricane Francine will bring strong winds and heavy rain to Louisiana. Francine will be capable of causing serious damage. Widespread outages of electricity are likely. Heavy rain is likely to cause flash floods.  The heaviest rain will fall as the center of Francine’s circulation approaches a given location.  Hurricane Francine will also drop heavy rain over parts of Mississippi, South Alabama and Northwest Florida as it moves inland.

Flood Watches are in effect for parts of Louisiana, Mississippi, South Alabama and Northwest Florida.

Hurricane Francine could cause a storm surge of up to 10 feet (3 meters) along parts of the coast of Louisiana.  The highest surge will occur just to the east of where the center of Francine makes landfall in southeast Louisiana.  The storm surge will continue after the center of Hurricane Francine makes landfall because southerly winds will continue to push water toward the coast.

A Storm Surge Warning is in effect for the portion of the coast from Cameron, Louisiana to the Mississippi/Alabama border.  The Storm Surge Warning includes Vermilion Bay, Lake Pontchartrain and Lake Maurepas.

 

Typhoon Yagi Brings Wind and Rain to Northern Vietnam

Typhoon Yagi brought wind and rain to northern Vietnam on Saturday.  At 5:00 a.m. EDT on Saturday the center of Typhoon Yagi was located at latitude 21.1°N and longitude 106.5°E which put the center about 65 miles (105 km) east of Hanoi, Vietnam.  Yagi was moving toward the west-northwest at 16 m.p.h. (26 km/h).  The maximum sustained wind speed was 125 m.p.h. (200 km/h) and there were wind gusts to 155 m.p.h. (200 km/h).  The minimum surface pressure was 942 mb.

Typhoon Yagi was the equivalent of a major hurricane when it made landfall on the northern coast of Vietnam near Haiphong.  A small circular eye was present at the center of Yagi’s circulation.  The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms.  The strongest winds moved over the coastal regions of northern Vietnam.  Bands of showers and thunderstorms revolved around the core of Yagi’s circulation.  Storms dropped heavy rain on northern Vietnam.

‘Winds to typhoon force extended out 50 miles (80 km) from the center of Typhoon Yagi.  Winds to tropical storm force extended out 180 miles (290 km) from the center of Yagi’s circulation.

The Hurricane Intensity Index (HII) for Typhoon Yagi was 23.6.  The Hurricane Size Index (HII) was 20.6 and the Hurricane Wind Intensity Size Index (HWISI) was 44.2.  Typhoon Yagi was similar in size and intensity to Hurricane Jeanne when Jeanne hit southeast Florida in 2004.

Typhoon Yagi will move around the southern part of a high pressure system over China.  The high pressure system will steer Yagi toward the west-northwest during the next 24 hours.  On its anticipated track, Typhoon Yagi will move across northern Vietnam.  The center of Typhoon Yagi will pass near Hanoi in a few hours.

Typhoon Yagi will weaken gradually as it moves farther inland over northern Vietnam.  Yagi will bring strong winds and heavy rain to northern Vietnam during the next 24 hours.  Yagi is capable of causing major damage.  Heavy rain will cause floods in many locations.  Widespread outages of electricity are likely.

 

Typhoon Yagi Hits Hainan

Typhoon Yagi hit Hainan on Friday morning.  At 11:00 a.m. EDT on Friday the center of Typhoon Yagi was located at latitude 20.2°N and longitude 109.8°E which put the center about 25 miles (40 km) west of Haikou, China.  Yagi was moving toward the west-northwest at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 140 m.p.h. (220 km/h) and there were wind gusts to 165 m.p.h. (265 km/h).  The minimum surface pressure was 928 mb.

Typhoon Yagi brought strong winds and heavy rain to Hainan on Friday morning.  The core of Typhoon Yagi moved over the northeastern part of Hainan.  A small circular eye was present at the center of Yagi’s circulation.  The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms.  The strongest winds moved over the northern coastal regions of Hainan.  Bands of showers and thunderstorms revolved around the core of Yagi’s circulation.  Storms dropped heavy rain on Hainan and southern China.

The formation of concentric eyewalls on Thursday caused the size of Typhoon Yagi’s circulation to increase.  Winds to typhoon force extended out 70 miles (110 km) from the center of Yagi’s circulation.  Winds to tropical storm force extended out 185 miles (300 km) from the center of Typhoon Yagi.

The Hurricane Intensity Index (HII) for Typhoon Yagi was 28.3.  The Hurricane Size Index (HII) was 24.9 and the Hurricane Wind Intensity Size Index (HWISI) was 53.2.  Typhoon Yagi was similar in size to Hurricane Jeanne when Jeanne hit southeast Florida in 2004.  Yagi was stronger than Jeanne was.

Typhoon Yagi will move through an environment that will be somewhat favorable for intensification during the next 12 hours.  The center of Yagi’s circulation will move over water where the Sea Surface Temperatures are near 30°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  However, Typhoon Yagi may not intensify during the next 12 hours because the core of Yagi’s circulation was somewhat disrupted as it moved across Hainan.

Typhoon Yagi will move around the southern part of a high pressure system over China.  The high pressure system will steer Yagi toward the west-northwest during the next 24 hours.  On its anticipated track, the center of Typhoon Yagi will reach northeastern Vietnam in 12 hours.  Typhoon Yagi could still be the equivalent of a major hurricane when it reaches VIetnam.

Typhoon Yagi will continue to produce strong winds and heavy rain in parts of Hainan during the  next few hours.  Yagi will be capable of causing major damage in Hainan.  Heavy rain is likely to cause floods in some locations. Typhoon Yagi will also produce strong winds and heavy rain in parts of southern China.  Yagi will produce strong winds and heavy rain in southwestern Guangdong and Guangxi.  Typhoon Yagi will bring strong winds and heavy rain to northeastern Vietnam during the weekend.  Yagi is likely to cause floods in northeastern Vietnam.  Typhoon Yagi could also cause a storm surge of up to 10 feet (3 meters) along the coast of northeastern Vietnam.

Typhoon Yagi Passes South of Hong Kong

Powerful Typhoon Yagi passed south of Hong Kong on Thursday.  At 5:00 p.m. EDT on Thursday the center of Typhoon Yagi was located at latitude 19.3°N and longitude 112.5°E which put the center about 230 miles (370 km) south-southwest of Hong Kong.  Yagi was moving toward the west at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 150 m.p.h. (240 km/h) and there were wind gusts to 185 m.p.h. (295 km/h).  The minimum surface pressure was 923 mb.

The inner end of a rainband wrapped around the original eye and eyewall at the core of Typhoon Yagi and concentric eyewalls formed.  The formation of concentric eyewalls ended the intensification of Typhoon Yagi, but Yagi was still the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale.

A circular eye with a diameter of 23 miles (37 km) was at the center of Yagi’s circulation.  The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms.  A second outer ring of thunderstorms surrounded the inner eyewall.  Bands of showers and thunderstorms were revolving around the core of Typhoon Yagi.  Storms near the core of Yagi generated upper level divergence that pumped mass away from the typhoon.

The formation of concentric eyewalls caused the size of Typhoon Yagi’s circulation to increase.  Winds to typhoon force extended out 90 miles (145 km) from the center of Yagi’s circulation.  Winds to tropical storm force extended out 205 miles (330 km) from the center of Typhoon Yagi.

The Hurricane Intensity Index (HII) for Typhoon Yagi was 31.6.  The Hurricane Size Index (HII) was 24.8 and the Hurricane Wind Intensity Size Index (HWISI) was 56.4.  Typhoon Yagi was similar in intensity to Hurricane Laura when Laura hit southwest Louisiana in 2020.  Yagi is bigger than Laura was.

Typhoon Yagi will move through an environment that will be favorable for intensification during the next 12 hours.  Yagi will move over water where the Sea Surface Temperatures are near 30°C.  It will move under the middle of an upper level ridge over the South China Sea.  The upper level winds are weak near the middle of the ridge and there will be little vertical wind shear.  Even though Typhoon Yagi will move through a favorable environment, the concentric eyewalls may prevent Yagi from intensifying.  If the inner eyewalls weakens, then Typhoon Yagi could weaken as well.  If the inner eyewall remains intact, then Typhoon Yagi could intensify during the next few hours.

Typhoon Yagi will move around the southern part of a high pressure system over China.  The high pressure system will steer Yagi toward the west during the next 24 hours.  On its anticipated track, the center of Typhoon Yagi will reach northeastern Hainan in 12 hours.  Typhoon Yagi is likely to be the equivalent of a major hurricane when it reaches Hainan.

Typhoon Yagi will bring strong winds and heavy rain to Hainan.  Yagi will be capable of causing major damage in Hainan.  Heavy rain is likely to cause floods in some locations.  Typhoon Yagi could also cause a storm surge of up to 14 feet (4.3 meters) along the coast of northeastern Hainan.  Yagi will also bring strong winds and heavy rain to southwestern Guangdong and Guangxi.

 

Typhoon Yagi Rapidly Intensifies to Equivalent of a Major Hurricane

Typhoon Yagi rapidly intensified to the equivalent of a major hurricane over the South China Sea on Wednesday.  At 11:00 a.m. EDT on Wednesday the center of Typhoon Yagi was located at latitude 19.2°N and longitude 116.6°E which put the center about 275 miles (445 km) southeast of Hong Kong.  Yagi was moving toward the west at 6 m.p.h. (10 km/h).  The maximum sustained wind speed was 125 m.p.h. (200 km/h) and there were wind gusts to 155 m.p.h. (250 km/h).  The minimum surface pressure was 968 mb.

Typhoon Yagi rapidly intensified to the equivalent of a majoro hurricane on Wednesday.  A circular eye was visible at the center of Yagi’s circulation.  The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Typhoon Yagi.  Storms near the core generated upper level divergence that pumped large amounts of mass away from the typhoon.  The removal of large amounts of mass caused the surface pressure to decrease rapidly.

The circulation around Typhoon Yagi increased in size as Yagi intensified rapidly.  Winds to typhoon force extended out 60 miles (95 km) from the center of Yagi’s circulation.  Winds to tropical storm force extended out 140 miles (220 km) from the center of Typhoon Yagi.

The Hurricane Intensity Index (HII) for Typhoon Yagi was 23.6.  The Hurricane Size Index (HSI) was 16.2 and the Hurricane Wind Intensity Size Index (HWISI) was 39.8.  Typhoon Yagi was similar in intensity to Hurricane Dennis when Dennis hit Florida in 2005.  Yagi is larger than Dennis was.

Typhoon Yagi will move through an environment that will be very favorable for intensification during the next 24 hours.  Yagi will move over water where the Sea Surface Temperatures are near 30°C.  It will move under the middle of an upper level ridge over the South China Sea. The upper level winds are weak near the middle of the ridge and there will be little vertical wind shear.  Typhoon Yagi will intensify during the next 24 hours.  Yagi could continue to intensify rapidly during the next few hours.  If the inner end of rainband wraps around the eye and eyewall in the core of Yagi’s circulation, then an eyewall replacement cycle could cause Typhoon Yagi to weaken.

Typhoon Yagi will move around the southern part of a high pressure system over China.  The high pressure system will steer Yagi toward the west-northwest during the next 24 hours. On its anticipated track, the center of Typhoon Yagi will be south of Hong Kong in 24 hours.  Yagi will approach Hainan and the coast of southern China in 36 hours.  Typhoon Yagi is likely to be the equivalent of a major hurricane when it approaches Hainan and the coast of southern China.

Typhoon Yagi will bring strong winds and heavy rain to southern China later this week.  Yagi will bring strong winds and heavy rain to Guangdong, Guangxi and Hainan.  Heavy rain is likely to cause floods in some locations.

 

Typhoon Shanshan Brings Wind and Rain to Kyushu

Typhoon Shanshan brought wind and rain to Kyushu on Wednesday.  At 5:00 p.m. EDT on Wednesday the center of Typhoon Shanshan was located at latitude 31.6°N and longitude 130.2°E which put the center about 35 miles (55 km) west of Kagoshima, Japan.  Shanshan was moving toward the north at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 100 m.p.h. (160 km/h) and there were wind gusts to 120 m.p.h. (195 km/h).  The minimum surface pressure was 957 mb.

Typhoon Shanshan brought wind and rain to Kyushu on Wednesday.  The eastern side of the eyewall of Shanshan moved over Makurazaki, Japan.  A weather station in Makurazaki reported a sustained wind speed of 69 m.p.h. (111 km/h).  The weather station also reported 8.42 inches (214 mm) of rain.  A weather station in Kaseda reported 10.95 inches (278 mm) of rain.  A weather station in Ibusuki reported 9.33 inches (237 mm) of rain.

Typhoon Shanshan was weakening gradually when it reached the west coast of Kyushu.  An upper level trough over northeastern Asia was producing southwest winds that were blowing toward the top of Shanshan’s circulation.  Those winds caused more vertical wind shear.  The increase in wind shear caused Typhoon Shanshan to start to weaken.

An eye was no longer visible at the center of Typhoon Shanshan on conventional satellite images.  The former eye was still being detected by radars operated by the Japan Meteorological Agency.  There were breaks in the ring of thunderstorms that surrounded the former eye.  The strongest winds were still occurring in that broken ring of storms.  Bands of showers and thunderstorms were revolving around the core of Typhoon Shanshan.

The circulation around Typhoon Shanshan was still symmetrical.  Winds to typhoon force extended out 30 miles (50 km) from the center of Shanshan’s circulation.  Winds to tropical storm force extended out 125 miles (200 km) from the center of Typhoon Shanshan.

The Hurricane Intensity Index (HII) for Typhoon Shanshan was 16.5.  The Hurricane Size Index (HSI) was 11.8 and the Hurricane Wind Intensity Size Index (HWISI) was 28.3.  Typhoon Shanshan was similar in intensity to Hurricane Idalia when Idalia hit Florida in 2023.  Shanshan was bigger than Idalia was.

Typhoon Shanshan will move around the western end of a high pressure system over the Western North Pacific Ocean.  The high pressure system will steer Shanshan toward the north during the next 12 hours.  The upper level trough over northeastern Asia will steer Shanshan toward the northeast on Thursday.  On its anticipated track, the center Typhoon Shanshan will move near the west coast of Kyushu during the next 12 hours.  Shanshan will move inland over Kyushu on Thursday.

Typhoon Shanshan will weaken gradually as it moves inland over Kyushu.  Even though Shanshan will weaken it will still produce strong winds and drop heavy rain over much of Kyushu.  Heavy rain is likely to cause flash floods in some locations,